1. Field of the Invention
The present invention relates to an electrically conductive, plasma-resistant member that is resistant to erosion by halogen-based plasmas and has a coating endowed with electrical conductivity, wherein at least part of the member to be exposed to plasma has formed thereon by thermal spraying a coating made of yttrium metal, a mixture of yttrium metal and yttrium oxide, a mixture of yttrium metal and yttrium fluoride, or a mixture of yttrium metal, yttrium oxide and yttrium fluoride. Such members may be suitably used as, for example, components or parts exposed to a plasma in semiconductor manufacturing equipment or in flat panel display manufacturing equipment (e.g., equipment for manufacturing liquid crystal displays, organic electroluminescent devices or inorganic electroluminescent devices).
2. Prior Art
To prevent contamination of the workpieces by impurities, semiconductor manufacturing equipment and flat panel display manufacturing equipment (e.g., equipment for manufacturing liquid crystal displays, organic electroluminescent devices and inorganic electroluminescent devices) which are used in a halogen-based plasma environment are expected to be made of materials having a high purity and low plasma erosion.
Equipment such as gate etchers, dielectric film etchers, resist ashers, sputtering systems, and chemical vapor deposition (CVD) systems are used in semiconductor manufacturing operations. Equipment such as etchers for fabricating thin-film transistors are used in liquid crystal display manufacturing operations. These manufacturing systems are being equipped with plasma generators to enable fabrication to smaller feature sizes and thus achieve higher levels of circuit integration.
In the course of these manufacturing operations, halogen-based corrosive gases such as fluorine-based gases and chlorine-based gases are employed in the above equipment on account of their high reactivity.
Examples of fluorine-based gases include SF6, CF4, CHF3, ClF3, HF, and NF3. Examples of chlorine-based gases include Cl2, BCl3, HCl, CCl4 and SiCl4. These gases are converted to a plasma by introducing microwaves or radio-frequency waves to an atmosphere containing the gas. Members of a piece of equipment that are exposed to such halogen-based gases or their plasmas are required to have a high resistance to erosion.
To address such a requirement, coatings of ceramic, such as quartz, alumina, silicon nitride or aluminum nitride and anodized aluminum coatings have hitherto been used as materials for imparting members with erosion resistance to halogen-based gases or plasmas thereof. Recently, use is also being made of members composed of stainless steel or Alumite-treated aluminum whose plasma resistance has been further enhanced by thermally spraying yttrium oxide thereon (JP-A 2001-164354).
However, the surface of such components whose plasma resistance is to be improved is often an electrical insulator. Efforts to improve the plasma resistance result in the interior of the plasma chamber becoming coated with the insulator. In such a plasma environment, at higher voltages, abnormal electrical discharges sometimes arise, damaging the insulating film on the equipment and causing particles to form, or the plasma-resistant coating peels, exposing the underlying surface that lacks plasma resistance and leading to an abrupt increase in particles. The particles that have broken off in this way off deposit in such places as the semiconductor wafer or the vicinity of the bottom electrode, adversely affecting the etching accuracy and thus compromising the performance and reliability of the semiconductor.
Although the purpose for improvement differs from that in the present invention, JP-A 2002-241971 discloses a plasma-resistant member in which the surface region to be exposed to a plasma in the presence of a corrosive gas is formed of a layer of a periodic table group IIIA metal. The film thickness is described therein as about 50 to 200 μm. However, the examples provided in that published document describe film deposition by a sputtering process. Application of such a process to actual members would be extremely difficult, both economically and technically. Hence, such an approach lacks sufficient practical utility.